Connecticut has fought against these foreign intruders for decades. Washington has been a key player, supporting local and state efforts through the Army Corps of Engineers, the U.S. Forest Service, and the interagency Aquatic Nuisance Species Task Force.

But the proposed 2018 Trump administration budget has torn that involvement out by the roots. It defunds the Army Corps’ $9 million Aquatic Plant Control Research Program and cuts more than half the money out of the U.S. Forest Service effort aimed at combating invasive species.

Officials and lawmakers say that without federal help, local efforts to keep invaders from spreading may be in jeopardy. A $45,000 annual grant from the Aquatic Nuisance Species Task Force helps the state’s Department of Energy and Environmental Protection deploy a force of inspectors at boat launches, including Candlewood Lake.

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Persicaria perfoliata, has been found.

Southwest

Connecticut

Greenwich

Stamford

New Canaan

Norwalk

Westport

Wilton

Weston

Fairfield

Stratford

Milford

Monroe

Ridgefield

Redding

Danbury

Bridgewater

Brookfield

Newtown

Southbury

Roxbury

Woodbury

Central, southern Connecticut

New Haven

Branford

Hamden

North Haven

Wallingford

Prospect

Meriden

Middletown

Middlefield

Madison

Old Saybrook

Lyme

Elsewhere

Also found in Torrington, Colchester, Groton and elsewhere.

The inspectors inform boat owners at launches about rules governing removal of residual plants from the undersides of vessels. The aim is to prevent inadvertent transport of fast-growing aquatic weeds like hydrilla and milfoil into so-far unpolluted waters.

The Trump budget cuts the Forest Service’s Urban and Community Forest Program, which has provided Connecticut with $230,000 a year to pay for an urban forester and give grants to municipalities for tree inventories, replanting and general understanding of invasive species.

“Without it, we have no program,” said Christopher Martin, DEEP’s director of forestry. “The impact could be municipalities don’t have the information they need, so they make poor choices because no one is there to explain how to do it.”

“In Connecticut, we pride ourselves on our excellent quality of life, supporting a clean environment and protecting natural wonders,” she said. “It may not be as spectacular as Yosemite, but it’s important to us. We want to make sure our ecosystems are healthy, our water is clean and we can teach kids to fish in lakes where our grandparents taught us.”

Whether plant, animal or insect, invasive species cost the U.S. some $120 billion annually in damages, according to one oft-quoted analysis.

The Connecticut Invasive Plant Working Group lists 97 species of plants already at work or threatening Connecticut.

Including insects, these are among the most common:

Emerald ash borer, the little green devourer of ash trees. Unknown in Connecticut prior to 2012, it has proliferated particularly in the eastern part of Fairfield County, the southern part of Litchfield County and all of New Haven County. Once infected, ash trees die and must be cut down. They represent 10 percent to 15 percent of trees in western Connecticut forests, Martin said.

Japanese knotweed, mile-a-minute, purple loosestrife and other vine-like species — many of them brought over from Asia as ornamental plants. They grow like wildfire in local gardens, forests, highway rights-of-way and rural property.

Milfoil (technically Eurasian watermilfoil), the bane of boaters, swimmers and fishers at Candlewood Lake and other fresh-water bodies and rivers in the state. It grows in shallower parts, sucking out nutrients and thereby posing a threat to trout and other fishermen’s favorites. Of Candlewood Lake’s 5,200 acres, between 600 and 700 are infested with milfoil.

It is no coincidence that the uptick of invasives in recent decades occurred alongside globalization of the economy and the rise of international trade — particularly with Asia.

The emerald ash borer, for instance, arrived in the U.S. as a hitchhiker inside wooden shipping pallets and packing crates bearing Asian imports.

Early detection is the key to eradicating invasive species, biologists say. If an infestation is caught early, it can be prevented from spreading.

Connecticut scientists also are experimenting with government-approved methods of using insects and fish to control the spread of some attackers.

Triploid grass carp have been introduced to Candlewood Lake to eat up milfoil. Also, controlled releases of weevils have been aimed at mile-a-minute vines, which stick like Velcro to plants and trees. Beetles have been set loose on purple loosestrife.

“They are beneficial bugs that feed on plants,” said Ellis, who added the Army Corps of Engineers helped raise the insects and supervise their release.

It is still too early to say whether the counterattack is working.

“Where we find new growth of MAM, we see the weevils have found it first,” said Kathleen Nelson, of New Milford, a former college-level biology teacher and founder of Mad Gardeners Inc. “It’s hard to know to what extent they’re helping, but we think they are.”